Exhibit 24 POWER OF ATTORNEY KNOW ALL PERSONS BY THESE PRESENTS, that the undersigned Directors of Aluminum Company of America (the "Company") hereby constitute and appoint JAN H. M. HOMMEN, MARY L. AMBROSE, EARNEST J. EDWARDS and BARBARA S. JEREMIAH, or any of them, their true and lawful attorneys and agents to do any and all acts and things and execute any and all instruments which said attorneys and agents, or any of them, may deem necessary or advisable or may be required to enable the Company to comply with the Securities Act of 1934, as amended, and any rules, regulations or requirements of the Securities and Exchange Commission in respect thereof, in connection with the registration under said Act of the Company's Annual Report on Form 10-K for 1993, including specifically, but without limiting the generality of the foregoing, power and authority to sign the name of the undersigned Directors of the Company to the Company's Annual Report on Form 10-K for 1993 to be filed with the Securities and Exchange Commission and to any instruments or documents filed as part of or in connection with any such Form 10-K; and the undersigned hereby ratify and confirm all that said attorneys and agents, or any of them, shall do or cause to be done by virtue hereof. IN WITNESS WHEREOF, the undersigned have subscribed these presents on the date set opposite their names below. /s/KENNETH W. DAM January 14, 1994 Kenneth W. Dam /s/JOHN P. DIESEL January 14, 1994 John P. Diesel /s/JUDITH M. GUERON January 14, 1994 Judith M. Gueron /s/JOSEPH T. GORMAN March 11, 1994 Joseph T. Gorman /s/JOHN P. MULRONEY January 14, 1994 John P. Mulroney /s/SIR ARVI PARBO January 14, 1994 Sir Arvi Parbo /s/FORREST N. SHUMWAY January 14, 1994 Forrest N. Shumway /s/FRANKLIN A. THOMAS January 14, 1994 Franklin A. Thomas